Although load weighing scales have been used extensively, throughout the years the use of scales in a high speed sheet conveying apparatus has not been common practice. In a device such as a mailing machine, mailpieces are conveyed in series past a number of stations for performing tasks in the processing of the mailpieces. These tasks could include placing inserts into an envelope, sealing the envelope to form a mailpiece, and placing a postage meter indicia on the mailpiece. In order to determine the amount of postage required, the mailpiece must first be weighed. A weighing scale for performing such a task should be able to operate at least at the same speed as the other components in the system, this usually being in excess of one mailpiece a second.
Scales capable of such high speed operation have recently been commercialized, as for example in the Paragon mail processor available from Pitney Bowes Inc. High speed scales have also been described in patents, see for example U.S. Pat. No. 4,856,602; 4,848,492 and 4,836,311. Although these scales have proven successful, a need for greater protection in the case of overload on the platform of the scale is needed. Overload protection is generally provided for scales when a load is dropped normal to the weighing platform, but it has been found that protection is also required to protect the scale for loads dropped on the edges of the platform or when one attempts to lift a scale by holding the platform.